Quick -Action Tensioning Device

ABSTRACT

A tensioning device for at least one cable control switch is described. The tensioning device includes a holding element for clamping and securing a cable thereto. A housing is connected to the holding element. An adjustment device is disposed between the housing and the holding element to permit adjustment between the housing and the holding element, thereby permitting a predetermined tension to be applied to the cable. The device also includes an electronic device for detecting the tension in the cable and for generating a signal indicative of the tension.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a United States Non-Provisional patent application that relies for priority on German Patent Application No. 20 2007 013 591.2, filed on Sep. 28, 2007, the contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a quick-action tensioning device for cable control switches, with a holding element to which a cable can be secured in a clamping manner, and a housing which is connected to the holding element, means for adjusting being provided between the housing and holding element in order to set a predetermined tension.

BACKGROUND OF THE INVENTION

U.S. Pat. No. 5,003,135 discloses a tensioning device for a safety switch in which a cable control is secured to an eyelet. The eyelet is connected to a threaded sleeve into which is screwed a threaded bolt which is in turn coupled to the safety switch. For setting the cable tension, an adjustment can be carried out between the threaded bolt and eyelet. In mechanical quick-action tensioning devices of this type, there is the problem that a drop in cable tension or excess tension is detected only relatively late via optical display means and therefore subsequent tensioning takes place only when the cable control switch has usually already been triggered, thus shutting down a machine or production plant. The maintenance and attention that these quick-action tensioning devices require are comparatively costly.

It is therefore the object of the present invention to provide a quick-action tensioning device for cable control switches that is easy to maintain and can signal a drop or rise in tension in good time.

SUMMARY OF THE INVENTION

It is, therefore, one aspect of the invention to address one or more of the deficiencies noted above.

According to the invention, the quick-action tensioning device has an electronic device for detecting the tension, by means of which device a signal can be generated to a controller if the tension deviates from a range of setpoints. It can thus be detected in good time if the tension of the cable becomes too great or too slack. Long before a cable control switch is triggered, it is thus possible to issue a warning in order then to adjust the cable tension. There is no need optically to monitor the cable tension at regular intervals.

For precise detection of the cable tension, the electronic device preferably comprises an optical sensor. The optical sensor can in this case be arranged and protected in a housing and can detect the movement of at least one bracing coupled to the cable. In this case, the bracing can be pivotably mounted on the housing, thus allowing a suitable ratio to be set between the cable tension and pivoting movement.

According to a further configuration of the invention, the direction of movement of the cable can also be detected by means of the sensor. It is thus possible to issue a signal indicating whether the cable is tensioned too much or too little.

Preferably, the controller is connected to a temperature sensor and an error signal with regard to the tension is output as a function of temperature. Especially in production plants, temperature fluctuations can occur, so that when a cable is tensioned for a long time, changes in tension can occur as a result of fluctuations in temperature. Such changes in tension as a function of the temperature can be compensated for via the controller using a temperature sensor, so that changes in tension based on changes in temperature can be detected but classified as harmless.

Other aspects of the invention will be made apparent from the description that follows and from the drawings appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described hereinafter in greater detail based on an exemplary embodiment and with reference to the appended drawings, in which:

FIG. 1 is a perspective view of a quick-action tensioning device according to the invention;

FIG. 2 is a view of the quick-action tensioning device when installed; and

FIG. 3 is a detailed view of the means for detecting the cable tension of the quick-action tensioning device.

DESCRIPTION OF EMBODIMENT(S) OF THE INVENTION

While one or more embodiments of the invention are described herein, the invention is not intended to be limited thereby. Instead, there are equivalents and variations, as should be appreciated by those skilled in the art that are also intended to fall within the scope of the invention.

A quick-action tensioning device 1 for a cable control switch comprises a holding element 2 to which a cable 3 can be secured. For this purpose, the cable 3 is tensioned between a plate 4 and the body of the holding element 2, wherein the plate 4 can be secured via a screw 5, thus clamping deflection of the cable 3 between the plate 4 and holding element 2.

Also provided, for fine adjustment of the tension of the cable 3, is a knurled nut 10 which can be used to vary the distance between the holding element 2 and a housing 8. The knurled nut is, in this case, connected to a shank 9 via a thread. An optical display 11 for the cable tension can be provided on the housing 8, a marking being attached to a viewing window 12. The mark can be displayed via a movable strip 13 to indicate whether the tension of the cable is too high or too low.

Also provided is a housing 14 of a cable control switch. The housing 14 has a triggering button 15, so that switching can take place in the event of the tension of the cable 3 deviating from a range of setpoints. Switching also can take place manually by pressing the switch 15.

FIG. 2 shows the quick-action tensioning device when installed. The cable 3 is guided via a plurality of eyelets 6 which are each secured to a holder 7, wherein the cable 3 can, for example, be tensioned around a machine. Provided at the end of the cable 3 is a further quick-action tensioning device with a holding element 2 having a knurled nut 10 for fine adjustment and also an eyelet 16 which is coupled to a pulling element 17. The pulling element 17 is connected via a spring 18 to a holder 19 which is secured to a fixed attachment or a wall 20.

Provided in the housing 14 of the cable control switch is an electronic device for detecting the tension, by means of which device a signal can be generated to a controller 22 via a line 21 if the tension deviates from a range of setpoints. If, for example, the tension of the cable 3 is increased as a result of an accident, the corresponding machine is switched off via the cable control switch 14. It can, however, also occur that during operation, as a result of an extension of the cable 3 and other factors, the cable tension drops but there is no emergency situation. Then, if the cable tension drops out of a range of setpoints, a signal can be issued to the controller 22 in good time via the electronic means, indicating that the cable tension should be adjusted. For this purpose, the controller 22 can be connected to a display device 23.

In addition, the controller 22 can be coupled to a temperature sensor, thus allowing a change in length as a result of deviations in temperature to be detected, wherein the range of setpoints can then be adjusted accordingly on the controller as a function of the temperature.

FIG. 3 shows in detail the device for detecting the cable tension. A bracing 30 is mounted so as to be able to pivot about an axis 31 and coupled to the cable 3 via various components, so that the bracing 30 is moved in the event of a change in the cable tension. In the tensioned state, an optical gap is interrupted by the bracing 30. If the tension of the cable 3 changes, the optical gap is cleared and a signal is issued to the controller 22. In this case, an optical sensor 33 is provided on a holding device 32. A plurality of gaps in the form of recesses, windows or the like can also be provided in the bracing 30, wherein the direction of triggering can in addition also be seen. Furthermore, corresponding markings can also be used to detect the extent of the movement of the bracing.

With a second bracing, a redundant system can also be constructed with a separate gap.

In the illustrated exemplary embodiment, the optical detection system is shown merely schematically. It is of course also possible to provide other optical or magnetic sensors for detecting the cable tension. 

1-7. (canceled)
 8. A tensioning device for at least one cable control switch, comprising: a holding element for clamping and securing a cable thereto; a housing connected to the holding element; an adjustment device disposed between the housing and the holding element to permit adjustment between the housing and the holding element, thereby permitting a predetermined tension to be applied to the cable; and an electronic device for detecting the tension in the cable and for generating a signal indicative of the tension.
 9. The tensioning device of claim 8, wherein the electronic device comprises an optical sensor for detecting the tension on the cable.
 10. The tensioning device of claim 9, further comprising: a bracing disposed between the housing and the cable, wherein the optical sensor is disposed in the housing and detects movement of the bracing.
 11. The tensioning device of claim 10, wherein the bracing is pivotally mounted in the housing.
 12. The tensioning device of claim 8, wherein the electronic device comprises a sensor that detects a direction of movement of the cable.
 13. The tensioning device of claim 8, wherein the electronic device generates an error signal indicative of a deviation of the tension from a predetermined setpoint.
 14. The tensioning device of claim 13, wherein the predetermined setpoint comprises a range of setpoints.
 15. The tensioning device of claim 8, further comprising a controller that receives the signal generated by the electronic device.
 16. The tensioning device of claim 15, wherein the controller generates a signal concerning a deviation of the tension from a predetermined setpoint based on the signal generated by the electronic device.
 17. The tensioning device of claim 15, further comprising: a temperature sensor connected to the controller to detect a temperature and to provide a temperature signal to the controller, wherein the controller generates an error signal with respect to the tension on the cable as a function of temperature. 